Suppress deprecation warnings in Symfony 3

I'm currently upgrading from Symfony 2.8 to 3.4 (we use only LTS releases).

There are a lot of deprecations which will need some time to be resolved. In the meantime these messages cost a lot of memory in dev mode (sometimes even leading to OOM errors) and spam the logs (~3 MB per request), so I would like to disable them completely.

So far I found only solutions for the log spam (configure Monolog), but not for the memory problem.

There is NO call to Debug::enable(). Adding the call explicitly with appropriate error reporting level has no effect.

Disabling error_reporting for E_USER_DEPRECATED has no effect.

There is a similar question which got no responses: How to remove the deprecation warnings in Symfony 2.7? (the question is almost 3 years old, so I re-ask)

I investigated the Symfony source, but saw no possibility for changes either, as everything around error handling seems to be static.